In this study, the metal coordination ability of
alpha-cyclodextrin (α-CD) was
employed to complex gold and thus isolate and extract it from different matrices
of acid-digests of electronic waste and soil. The crude α-CD used was extracted
from cassava and yam starch of the non-edible plant species using E.coliα-cyclodextrin
glucanotransferase (α-CGTase), with yields ≥ 62%. The reaction was
monitored progressively by ultraviolet-visible spectroscopy and checked with
infrared spectroscopy (IR) for the presence of α-CD. The crude α-CD
extract without need for purification was refluxed with gold containing-electronic
waste and soil predigested in a mixture of NaBr/HNO3 for 4 - 7 days.
Recoveries of up to 22.9% and 70.8% gold were achieved from electronic waste
and soil, respectively using 0.1 M α-CD.
This approach is cheap, effective, and environmentally benign.
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